Semiconductor integrated circuit devices are typically tested both when the devices have been finished but exist in the form of a wafer and after final packaging when the devices are in the form in which they would be sold by the manufacturer. The first test is often referred to as wafer sort test and the second test is usually referred to as final test. The present invention is concerned with wafer sort testing.
The main items of equipment that are used in wafer sort testing are a semiconductor integrated circuit tester and a wafer prober. The tester includes a test head. The wafer prober presents a wafer incorporating devices to be tested to the test head and the tester tests the devices. Typically, the test head is positioned over the wafer prober using a test head manipulator so that alignment pins attached to the test head enter alignment bores formed in docking bars that are rigidly attached to the top plate of the wafer prober and the test head is docked to the wafer prober by engaging movable cams attached to the test head with follower bearings that are attached to the docking bars and displacing the cams to draw the test head towards the wafer prober. When the test head is docked to the wafer prober, a tester interface can deliver stimulus signals generated by the pin electronics to the device under test (DUT) and response signals produced by the DUT to the pin electronics.
A typical tester interface includes a probe interface board, a pogo tower and a probe card. The pogo tower comprises an array of double-ended spring probe pins, such as the pins that are commonly referred to as pogo pins, installed in a generally annular pogo tower body. The probe interface board is a circuit board having an array of contacts at its upper side for connection to suitable contacts of the pin electronics and having an array of contacts at its lower side for engaging individual pogo pins of the pogo tower. The probe card has an array of contacts at its upper side for engaging individual pogo pins and has probe tips at its lower side for engaging contact pads of the DUT. The probe interface board is clamped between the pogo tower and the test head whereas the probe card rests on the top plate of the wafer prober and is held between the pogo tower and the prober top plate when the test head is docked to the wafer prober.
Probe cards are device specific and therefore must be changed when the tester is used to test a different device. Further, testing causes wear and tear of a probe card and accordingly the probe card must be removed for repair and maintenance even if the tester continues to be used for testing the same device. Conventionally, the probe card is removed either by an automated mechanism built in to the wafer prober or by raising the test head so that the pogo tower does not interfere with access to the probe card and then removing the probe card from above the wafer prober.